Background:: After treatment with cisplatin-based chemotherapy for testicular cancer (TC), patients have higher prevalence of cardiovascular complications after long-term follow up. Little is known about acute cardiovascular effects of cisplatin-based chemotherapy. The aim of this study was to explore acute effects of chemotherapy on cardiac function in patients treated for TC. Methods:: Fourteen TC patients (age 34.6±12.3 years) were studied before and 3 months after start with cisplatin-based chemotherapy. Cardiac function was assessed with magnetic resonance imaging. Fasting glucose and insulin levels were measured and insulin sensitivity, reflected by the quantitative insulin sensitivity index (Quicki index), was calculated. Results:: Left ventricular (LV) end-diastolic volume and LV stroke volume (SV) significantly decreased from 192±27 to 175±26 ml (P<0.05) and 109±18 to 95±16 ml (P<0.05), respectively. The ratio of early and atrial filling velocities across the mitral valve, a parameter of diastolic heart function, decreased after chemotherapy from 1.87±0.43 to 1.64±0.45 (P<0.01). Metabolic parameters were unfavourably changed, reflected by a decreased Quicki index, which reduced from 0.39±0.05 to 0.36±0.05 (P<0.05). Conclusion:: Chemotherapy for TC induces acute alterations in diastolic heart function, paralleled by unfavourable metabolic changes. Therefore, early after chemotherapy, metabolic treatment may be indicated to possibly reduce long-term cardiovascular complications.